Refrigeration evaporator

ABSTRACT

A method of making an evaporator and the resultant evaporator. The resultant evaporator comprises a continuous serpentine tube having an inlet and an outlet. The serpentine tube includes at least one column of parallel tube runs. Each tube run is defined by at least one reverse bend. The column of parallel tube runs has an overall length defined by the distance between the outermost tube runs. The evaporator further comprises a plurality of inner fins attached to the individual tubes. Each inner fin extends between two tube runs defined by opposite ends of a reverse bend. The inner fins have a length less than the overall length the column of tube runs.

FIELD OF THE INVENTION

[0001] The present invention relates generally to a method of making aheat exchanger and to the resultant heat exchanger. More particularly,it relates to a finned typed heat exchanger and evaporator produced byinserting a serpentine tube bundle into a plurality of inner finsretained in a fixture at a staggered arrangement in which aninterference fit between the inner fins and the tube bundle retains theinner fins onto the tube bundle and then removing the tube bundle withthe inner fins attached from the fixture. The resultant evaporatorcomprises a serpentine tube bundle having a plurality of inner finsattached thereon wherein the inner fins are off-set to provide astaggered inner fin pattern.

[0002] Finned type heat exchangers are commonly used in a variety ofheat exchanger-type apparatus. Finned heat exchangers having a tubebundle of a serpentine arrangement and fins mounted on the tubes areused in condensers and evaporators of refrigeration units, airconditioning units and the like. The fins are attached to the tubebundle and increase the effective heat absorbing area over which airflow is directed, thus increasing the cooling efficiency of theevaporator.

BACKGROUND OF THE INVENTION

[0003] Several attempts have been made to increase the coolingefficiency of the evaporator by varying the arrangement of the tubepattern and fin shape. U.S. Pat. No. 4,580,623 discloses a heatexchanger having parallel rows of serpentine tube coils slanted in thesame direction and using ultra thin fins having a pattern embossedthereon to induce turbulence in the air flow over the evaporator.

[0004] Another method of arranging the serpentine tube coils to increasethe cooling efficiency of the evaporator is described in U.S. Pat. No.5,183,105. This construction has a continuous tube with a plurality ofreverse bends forming a plurality of parallel tube rows arranged in setsof two as determined by each of the respective reverse bends. The tubesin the tube bundle are arranged such that, when viewed in cross section,lines drawn between the centers of the sets of two tubes form aherringbone pattern.

[0005] While these methods increase the cooling efficiency of theevaporator by using the staggered arrangement of the tube bundle,further cooling efficiency can be obtained by a more efficientarrangement of the fins.

SUMMARY OF THE INVENTION

[0006] The present invention is directed to a method of making anevaporator and to the resultant evaporator. The evaporator comprises acontinuous serpentine tube having an inlet and an outlet. The serpentinetube includes at least one column of parallel tube runs. Each tube runis defined by at least one reverse bend. The column of parallel tuberuns has an overall length defined by the distance between the outermosttube runs. The evaporator further comprises a plurality of inner finsattached to the individual tubes. Each inner fin extends between twotube runs defined by opposite ends of a reverse bend. The inner finshave a length less than the overall length the column of tube runs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a cross-sectional view of a refrigerator cabinetdisposed within the freezer compartment including an evaporatoraccording to a preferred embodiment of the invention.

[0008]FIG. 2 is a front view of a tube bundle having three columns oftube runs.

[0009]FIG. 3 is a side view of the tube bundle having three columns oftube runs shown in FIG. 2.

[0010]FIG. 4 is a front view showing in detail an inner fin for a tubebundle having three columns of tube runs.

[0011]FIG. 5 is a cross-sectional view, as taken approximately along thelines 5-5.

[0012]FIG. 6 is a perspective view of a fixture for retaining inner finsin the desired configuration.

[0013]FIG. 7 is a perspective view of the fixture having inner finsinserted and retained therein.

[0014]FIG. 8 illustrates a tube bundle just prior to insertion into theinner fins retained in the fixture.

[0015]FIG. 9 is a front view of an evaporator having three columns oftube runs inserted into the inner fins.

[0016]FIG. 10 is a side view of the evaporator of FIG. 9 having threecolumns of tube runs inserted into the inner fins.

[0017]FIG. 11 is a side view of an alternative embodiment of a tubebundle having four columns of tube runs.

[0018]FIG. 12 is a front view of the alternative embodiment of the tubebundle having four columns of tube runs as shown in FIG. 11.

[0019]FIG. 13 is a side view of an alternative embodiment of anevaporator having four columns of tube runs inserted into the innerfins.

[0020]FIG. 14 is a front view of the alternative embodiment of theevaporator of FIG. 13 having four columns of tube runs inserted into theinner fins.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Evaporators are used in a variety of environments to exchangeheat between a first medium isolated from a second medium. FIG. 1 showsa typical refrigerator cabinet 10 having a freezer compartment 12 and arefrigeration compartment 14. Cold air for the freezer and refrigerationcompartments 12 and 14 is provided by an evaporator 16. The freezercompartment 12 is sealed closed by freezer door 18 having appropriateperimeter gaskets. The refrigeration compartment 14 is similarly sealedclosed by refrigeration door 20. An evaporator 16 in accordance with thepresent invention is placed in a passageway 22 and is used to cool theair drawn in the direction indicated by the arrow 24, over theevaporator 16 and discharged into both the refrigeration and freezercompartments 12 and 14 by a fan (not shown).

[0022] The evaporator 16 is placed in a high humidity environmentwherein cooling the air causes moisture to condense on the evaporator,resulting in the formation of frost and ice. As frost and ice gather onthe evaporator 16, a heater element 26 is actuated to melt ice and frostfrom the evaporator 16. The resultant water is collected on a collectingpan 28 and removed through a drain 30 from the refrigerator.

[0023] Referring now to FIGS. 2-10, the evaporator 16 comprises aserpentine tube bundle 32 and a plurality of inner fins 34 mounted onthe serpentine tube bundle 32. As shown in FIGS. 2 and 3, the serpentinetube bundle 32 is a continuous tube having an inlet 36 and an outlet 38with a plurality of reverse bends 40 forming three columns 42, 44 and 46of staggered and parallel rows of tube runs 48. It should be noted thatthe term “continuous tube” does not require the tube to be formed from asingle tube. The continuous tube can be several individual tubes joinedby abutting the ends together to form a continuous tube. The reversebends 40 bend the tube 180 degrees (as shown in FIG. 2) allowing thetube runs 48 in each column and between columns to be parallel. Eachreverse bend 40 also staggers the sequential tube run such that the nexttube run is not linearly inline with the previous tube run when the tubebundle is viewed from the side. Rather, every other tube run is linearlyinline. This offset of the tube runs 48 increases the surface area ofthe tube runs which are disposed in the path of the air drawn in forcooling, thus increasing convection heat transfer.

[0024] The rows of parallel and staggered tube runs 48 continue for anumber of rows to form a column of tube runs. At the end of the firstcolumn 42 of tube runs, an end reverse bend 50, extending generallyperpendicularly to the centerline 51 of the first column 42, bends thetube to start a second column 44 of tube runs. The second column 44 oftube runs 48 is formed of rows of parallel and staggered tube runs, asin the first column. However, the second column extends generally backtoward the start of the first column. Each tube run 48 of the secondcolumn 44 is situated directly behind a corresponding tube run of thefirst column 42. The spacing 52 between each of the tube run of thesecond column 44 and the corresponding tube run of the first column 42(directly in front of the tube run of the second column 44) isapproximately the same for each set of tube runs. Likewise, each reversebend of the second column 44 is situated directly behind and angled in asimilar direction as a corresponding reverse bend of the first column42. Similarly, a third column 46 of tube runs 48 is formed.

[0025] A plurality of inner fins are mounted onto the tube bundle forfurther increasing the effective heat absorbing area. The inner fins ofthe present invention are formed from continuous strips of metal, forexample, by stamping or rolling. FIG. 4 shows in detail a continuousstrip 33 of inner fins 34 for use with a serpentine tube bundle 32 ofthe preferred embodiment. The inner fins 34 are formed into continuousstrip 33 but are not separated at this stage. By not separating theindividual inner fins 34 at this stage, the continuous strips 34 can beeasily rolled up for storage or transfer to the next assembly stage, ifrequired.

[0026] Each inner fin 34 has three equally spaced slots 54 cut into theinterior surface of inner fin 34. The number of slots and the locationof the slots correspond to the number of columns of tube runs and thelocation of reverse bends 40 of the columns 42, 44 and 46. An enlargedradius 56 is formed at both terminal ends of each slot 54. The distance58 between the locus of the enlarged radius 56 is approximately equal tothe distance 60 (FIG. 3) between the center of the tube runs of theopposite ends of a reverse bend.

[0027] The diameter 62 of the enlarged radius 56 is slightly smallerthan the diameter 64 of the tubes 48 (FIG. 2), thus allowing theenlarged radius 56 to snuggly surround the tube upon mounting the innerfin 34 onto the tube bundle 32 and provide an interference fit thereto.The width 66 of the middle section 68 of the slot 54 is narrower thanthe diameter 62 of the enlarged radius 56. The narrower middle section68 of each slot 54 provides rigidity for retaining the inner fin 34 ontothe tube bundle 32 while still allowing sufficient clearance for thereverse bend 40 to slip past the slot 54.

[0028] The inner fin 34 is further provided with an embossment pattern70 surrounding the slot 54 for structurally reinforcing the inner fin,retaining the inner fin onto the tube bundle and providing turbulentflow of the air flowing over the inner fin. FIG. 5 is a cross-sectionalview of the inner fin 34 taken approximately along lines 5-5 of FIG. 4and through one of the enlarged radius 56, showing a side view of theembossment pattern 70. The embossment pattern 70 comprises a raisedridge 72 surrounding the slot and a tapered lip 74 surrounding theenlarged radius 56.

[0029] The raised ridge 72 provides the inner fin 34 with structuralrigidity around the slot 54. In addition, by providing a break from thesmooth surface of the inner fin 34, the raised ridge 72 increasesturbulence in the flow of the air flowing over the inner fin 34. Theturbulent flow increases the convention heat transfer and thus theefficiency of the evaporator 16.

[0030] The tapered lip 74 also provides structural rigidity to the innerfin 34. Furthermore, the tapered lip 74 allows the tube bundle 32 to beeasily inserted into the slot 54 while resisting withdrawal of the tub ebundle 32 from the slot 54 after the inner fin 34 has been installedonto the tube bundle 32. Once the inner fin 34 has been installed ontothe tube bundle 32, the terminal end 76 of the tap ere d lip 74 contactsthe outer surface of the tube 48. Upon applying force in the oppositedirection of the tapered lip, the terminal end 76 abuts the outersurface of the tube and prevents the tube bundle 32 from withdrawingfrom the slot 54.

[0031] A fin fixture 78 is used to modularly build up several individualinner fins 34 into a configuration capable of receiving the tube bundle32. The fixture 78 comprises a number of corresponding, oppositelydisposed channels 80 a, 80 b, 80 c, 80 d and 80 e defined therein. Onthe edges of each channel 80, a plurality of grooves are cut thereon toform fin retainers 82. The height, width and thickness of each finretainer 82 is slightly larger than the height, width and thickness ofinner fin 34. This allows the inner fins 34 to easily slip in and out ofthe fin retainers 82, while the fin retainers 82 are still able toorient and stack the inner fins 34 once the inner fins are inserted intothe fin retainers 82.

[0032] The fin retainers 82 are formed such that each fin retainer isparallel with the other fin retainers. Furthermore, each fin retainer 82is formed at an equal distance from the adjacent fin retainers. Thus,the spacing 86 between the fin retainers 82 is the same through out theentire fixture 78. The fin retainers 82 of each channel are offset fromthe fin retainers of the adjacent channels by approximately one-half thedistance of the spacing 86 between the fin retainers. This offset of thefin retainers would correspondingly offset the inner fins 34 installedonto the tube bundle. The purpose of the offset of the inner fins isdiscussed below.

[0033] Five continuous strips 33 a, 33 b, 33 c, 33 d and 33 e providethe inner fins to be inserted into the fin fixture 78. Each strip 33 iscut to desired length to form individual and separate inner fin 34. Thenumber of continuous strips 33 corresponds to the number of channels 80in the fin fixture 78.

[0034] After the individual inner fins 34 have been separated from strip33, they are inserted into the fin retainers 82 such that the taperedlips 74 of the inner fins 34 are all directed in the direction of theinsertion of the tube bundle. The inner fins 34 throughout the samechannel 80 are also arranged such that slots 54 of successive inner finsare all aligned. The alignment of the slots 54 as installed in the finretainers 82 corresponds to the angle of the reverse bends 40 of thetube bundle 32.

[0035]FIG. 7 shows the fin fixture 78 with the inner fins 34 inserted inthe fin retainers 82. The inner fins 34 inserted in the fin retainers ofeach channel 80 form a row 84 of inner fins 34. As shown in FIG. 7, theinstallation of an inner fin 34 is omitted for every other fin retainer82 in the last channel 80 a. This omission of the installation of aninner fin in every other fin retainer in essence increases the spacingbetween the inner fins installed in the last channel 80 a to be twice aslarge as the spacing between the inner fins installed in the otherchannels 80. The purpose of the increased spacing between the inner fins32 of the last row 84 a will be discussed below.

[0036] Referring now to FIG. 8, the inner fins 34 are inserted into thefin retainers 82 and the tube bundle 32 is inserted into slots 54 of theinner fins 34 in the direction of arrow 88, taking care that eachreverse bend is inserted into a slot 54 of the first inner fins 34 ineach column. The tapered lips 76 of each inner fin are also directed inthe direction of arrow 88. Therefore, the tapered lips 76 assist inguiding the tube bundle 32 during insertion of the tube bundle intoslots 54 of the inner fins 34. The tube bundle 32 is inserted at adistance such that the exposed length 90 the tube runs inserted throughthe inner fins is approximately one spacing 86 between the fin retainer62 greater than the exposed length 92 of the non-inserted tube runs(FIG. 9). As the insertion of the tube bundle 32 proceeds into adjacentfins 34, each slot is positioned and oriented to receive the reversebend 40 without excessive bending of the tube runs 48. Since thediameter 62 of the enlarged radius 56 of the inner fin 34 is slightlysmaller than the diameter 64 of the tube 48, an interference fit resultsbetween the enlarged radius and the tube 48 upon insertion of tubebundle 32 into the inner fins 34. This interference fit retains theinner fins 34 onto the tube bundle 32.

[0037] After the tube bundle 32 has been inserted through the slots 54of the inner fins 34, the tube bundle with the inner fins attached arethen removed from the fin fixture 78 in the direction of arrows 94.

[0038] Referring now to FIG. 9, the tube bundle 32 with the inner finsattached are then inserted into a single outer fin 96. As opposed to theinner fin having a length less than the overall length 98 of each column42,44 and 46 of tube runs, the single outer fin 96 has a length greaterthan the overall length 98 of the column of tube runs.

[0039] Similar to the inner fin 34, the outer fin 96 is formed from onecontinuous strip of metal. The outer fin 96 has three columns and fiverows of slots cut into the outer fin 96.

[0040] The number of slots and the location of the slots correspond tothe number of reverse bends 40 and the location of the reverse bendsinserted through the inner fins 34. The tube bundle is inserted throughthe outer fin 96 until the spacing 100 between the outer fin 96 and theoutermost inner fins 34 a is equal to the spacing 86 between the innerfins 34 of channels 80. In addition to increasing the effective heatabsorbing area, the single fin 96 also acts as a support at the end ofthe evaporator 16, thus eliminating the need for a bracket at the end ofthe evaporator 16.

[0041] The fin fixture of the present invention offers severaladvantages over using spacers to locate the inner fins duringinstallation of the tube bundle into the inner fins. First, the finfixture of the present invention allows identical inner fins to be usedfor different size evaporators. For instance, the preferred embodimentconsists of ten tube runs per column. Therefore, five channels providingfive rows of inner fins are required. Should an evaporator requiregreater cooling capacity, two additional tube runs could be added toeach column of the tube bundle to extend the length of the column. Toaccommodate for an increased number of tube runs, additional channelswould be added to the fin fixture. Since the distance between the tuberuns of first tube bundle, having ten tube runs per column, is the sameas the distance between the runs of the second tube bundle, havingtwelve tube runs per column, a common inner fin could be used in bothfixtures for making the two different size evaporators. Thisinterchangeability of the inner fins allows evaporators having differentcooling capacity to be built without having to increase the complexityof the inner fins. Other configurations of tubes and columns arepossible, depending on the application for which the evaporator will beused.

[0042] Another advantage of the fin fixture is the allowance of theplacement of the inner fins in one channel to be independent from theplacement of the inner fins in another channel, since each channel hasits own sets of fin retainers. The independence of the placement of theinner fins of one channel from another channel allows the inner finsaligned by one channel to be offset with the inner fins aligned byanother channel. Furthermore, the independence of the placement of theinner fins allows the spacing between the inner fins resulting from onechannel to be different the spacing between the inner fins resultingfrom another channel.

[0043] A third advantage of the fin fixture is the consistency of theplacement of and spacing between the inner fins of the resultingevaporator. The fin fixture is a rigid structure. Hence, the placementof the inner fins will be consistently evenly spaced on the resultingevaporator.

[0044]FIGS. 9 and 10 show the resulting evaporator 16. Inner fins 34 aremounted onto the tube bundle 32. Each inner fin 32 is retained on andextends between the tube runs of the opposite ends of a reverse bend 40.Since the fin retainers 82 of each channel 80 are equally spaced, theinner fins 34 of each row 84 are likewise equally spaced. The inner fins34 of each row 84 are offset from the inner fins of the adjacent row byapproximately one-half of the spacing 86 between the inner fins.Therefore, the inner fins of one row are situated behind the center ofthe spacing between the inner fins of the adjacent row. This offset ofthe inner fins 34 provides a staggered arrangement in the direction ofthe air flow as indicated by arrow 24. The staggered arrangement of theinner fin 34 increases the area of the inner fins coming in contact withthe air flow, thus increasing the convection heat transfer and theefficiency of the evaporator.

[0045] It is common knowledge in the industry that frost build up can becontrolled by varying the spacing between the inner fins 34. Since innerfins in the bottom row 84 a of inner fins come into contact with themoist air first, more frost tends to build up on the inner fins 34 ofthe bottom row 84 a than the inner fins of the other rows. For thisreason, the spacing between the inner fins of the bottom row 84 a isgreater than the spacing between the inner fins of other rows. Thisincreased spacing between the inner fins of the bottom row allows agreater amount of frost to be built up on the inner fins of the bottomrow while still allowing sufficient spacing for the air to travelthrough the frost buildup. This increased space between the fins allowsa greater time interval between the need to activate the heater element26 to melt the frost build up on the evaporator.

[0046] The usage of the five separate strips 33 for forming the finsallows the increased spacing between the inner fins 32 of the last row84 e without creating waste in fin material. Since each row 84 is formedfrom a separate continuous strip 33, the continuous strip 33 e forforming the last row 84 e will be consumed at a slower rate than thecontinuous strips for forming the other rows. Allowing the continuousstrips 33 to be consumed at different rates eliminates waste finmaterial or increased complexity compared to a process in which the finsare formed from one large sheet rather than five narrow strips. To allowfor an increased spacing between the fins at the end of the evaporatorif one large sheet is used for forming the fins, every other fin wouldneed to trimmed to allow the spacing between the fins at the end of theevaporator to be greater than the spacing between the fins at theremaining portion of the evaporator. This process of trimming the finshas the undesirable effect of creating waste fin material. Rather thantrimming the fins, another approach is to use two different sets ofinner fins. One set of fins would extend beyond the overall length ofthe column of tube runs. A second set of fins would be shortened at theend to define the increased spacing at the bottom of the evaporator.However, this approach is also undesirable since it would increase thecomplexity of the inner fins. By providing a separate continuous strip33 for each channel 80, the spacing between the inner fins at the end ofthe evaporator can be increased without creating wasted fin material orincreasing complexity.

[0047] The usage of individual strips 33 for each channel 80 for formingthe inner fins 32 also allows for varying the spacing between the innerfins 32 beyond the preferred embodiment as shown in FIGS. 7-10. Inaddition to increasing the spacing between the inner fins 32 b of thelast row 84 e, the spacing between the inner fins 32 of the other rows84 can also be increased by the omitting the installation of an innerfin 32 in every other fin retainer 82 for the desired channel 80. Thespacing between the inner fins 32 can be further increased by theomission of the installation of inner fins 32 in two or more consecutivefin retainers 82.

[0048] In addition to varying the spacing between the inner fins fromone row of inner fins with another row of inner fins, the spacingbetween the inner fins within the same row can also be varied. This canbe accomplished by selectively omitting the installation of an inner fin32 in certain predetermined fin retainers 82. Having the ability to varythe spacing between the inner fins within the same row offers severaladvantages over an evaporator having equal spacing between the fins.First, by having the ability to vary the spacing between the inner finswithin the same row, the spacing between the inner fins at one side ofthe evaporator can be greater than the spacing between the inner fins atthe other side of the evaporator. This fin arrangement allows for agreater build up of frost on one side of the evaporator while stillallowing sufficient spacing for the air to travel through the frostbuildup. This fin arrangement is particularly important when therefrigerator has a vegetable crisper. Since vegetables and fruitsgenerally contain a large amount moisture, the air drawn from thevegetable crisper will have a higher amount of moisture than the airdrawn the other portions of the refrigerator. Depending on the design ofthe air passages leading to the evaporator, the air drawn from thevegetable crisper may be directed more to one side of the evaporatorthan the other side of the evaporator. Therefore, the side of theevaporator in which the air from the vegetable crisper is drawn to willhave a greater amount of frost buildup. By increasing the spacingbetween the inner fins at the side the air from vegetable crisper isdrawn to allows the air to flow through the entire evaporator eventhough there is a greater amount of frost buildup at one side of theevaporator.

[0049] The ability to vary the spacing within the same row also allowsfor a shorter row of inner fins to be formed. This can be accomplishedby omitting the insertion of inner fins in the fin retainers 82 at oneend of the channel 80 and having shorter tube runs 48 which are to beinserted into the inner fins 32 of that channel 80. The formation of ashorter row of inner fins and tube runs allows the evaporator to beshaped in a non-rectangular shape thus allowing for clearance ofadjacent components, if necessary. For instance, a non-rectangularshaped evaporator allows for a notch to be formed at one side of theevaporator. A notched portion of the evaporator provides for thenecessary clearance for a mount for mounting the evaporator to therefrigerator while still allowing the remaining portions of theevaporator to extend throughout the air flow passage. A notched portionof the evaporator also provides for allows the necessary clearance toattached a sensor or control module on the evaporator while stillallowing the remaining portions of the evaporator to extend throughoutthe air flow passage.

[0050] In addition to increasing or decreasing the number of tube runsin each column to increase or decrease the cooling capacity of theevaporator, the width of the evaporator can also be varied to affect thecooling capacity of the evaporator. The latter can be achieved byincreasing or decreasing the number of columns.

[0051] FIGS. 11-14 shows an embodiment having a greater width. In thisalternative embodiment, the tube bundle 102 is formed with four columns104 of tube runs. The increased number of columns increases the width106 of the evaporator 108 and, hence, the cooling capacity of theevaporator 108.

[0052] This alternative embodiment also depicts a tube bundle 102 havingan odd number of tube runs 110 in each column 104. To accommodate forthe odd number of tube runs, the last row 112 of inner fins defines notonly slots aligned with the reverse bends 114 but also slots aligned toreceive end bends 116. Therefore, it is sometimes necessary to have theinner fins in one row different from the inner fins in the other rows.

[0053] Various features of the present invention have been describedwith reference to the preferred embodiment. It should be understood thatmodifications may be made to the method of making an evaporator and theresultant evaporator without departing from the spirit and scope of thepresent invention as represented by the following claims. For instance,the above embodiments depict every inner fin being offset from theproceeding inner fin in the adjacent row. An evaporator can be made withonly some inner fins offset from the proceeding inner fins in theadjacent row, while other inner fins are inline with the proceedinginner fins in the adjacent row. Such an evaporator would still takeadvantage of the increased convection heat transfer by staggering someof the inner fins.

1. An evaporator for disposition along an air flow for cooling the aircomprising: a continuous serpentine tube having an inlet and an outlet,said serpentine tube including at least one column of parallel pluraltube runs, each tube run being defined by at least one reverse bend,said column of parallel tube runs having an overall length defined bythe distance between the outermost tube runs of said column; and aplurality of inner fins attached to at least one of said tube runs, eachsaid inner fin extending between at least two tube runs defined byopposite ends of a reverse bend, said inner fins having an overalllength less than the overall length of said column of tube runs.
 2. Theevaporator according to claim 1 wherein said plurality of inner fins arearranged in at least two rows, wherein the inner fins within each roware equally spaced.
 3. The evaporator according to claim 2 wherein saidevaporator has first and second rows of inner fins, said first row ofinner fins being off-set from said second row of inner fins to provide astaggered inner fin pattern.
 4. The evaporator according to claim 2wherein said evaporator has a first and second rows of inner fins, thespacing between said first row of inner fins being greater than thespacing between said second row of inner fins.
 5. The evaporatoraccording to claim 1 further comprising an outer fin attached to saidserpentine tube, said outer fin having a length greater than the overalllength of the column of tube runs.
 6. The evaporator according to claim1 wherein said parallel tube runs defined by opposite ends of a reversebend are off-set to provide a staggered tube run pattern.
 7. Theevaporator according to claim 1 wherein said tubing is made of aluminum.8. A method of forming an evaporator comprising the steps of: providinga continuous tube; bending said tube into a serpentine tube pattern toinclude at least one column of parallel tube runs, each tube run definedby at least one reverse bend, said column of parallel runs having anoverall length defined by the distance between the outermost tube runs;providing a plurality of inner fins having a length less than theoverall length of said column of tube runs, each said inner fin havingat least one slot, wherein the slots in adjacent inner fins are alignedand oriented in identical directions to receive said reverse bend ofsaid serpentine tube; inserting at least one reverse bend of saidserpentine tube through said aligned set of slots in said plurality ofinner fins; and wherein each inner fin is retained on the tube runs ofthe opposite ends of the inserted reverse bend such that each inner finextends between the tube runs of the opposite ends of the insertedreverse bend.
 9. The method of forming an evaporator according to claim8 wherein said step of inserting reverse bend through said slots in saidplurality of inner fins further comprising inserting a first reversebend through the slots of a first set of inner fins and a second reversebend through the slots of a second set of inner fins, the inner finsretained on the tube runs defined by the opposite ends of said firstreverse bend being off-set with the inner fins retained on the tube runsdefined by the opposite ends of said second reverse bend to provide astaggered inner fin pattern.
 10. The method of forming an evaporatoraccording to claim 8 wherein said step of inserting reverse bend throughsaid slots in said plurality of inner fins further comprising insertinga first reverse bend through the slots of a first set of inner fins anda second reverse bend through the slots of a second set of inner fins,each inner fin retained on the tube runs defined by the opposite ends ofsaid first reverse bend being equally spaced with the adjacent innerfins retained on the tube runs defined by the opposite ends of saidfirst reverse bend, each inner fin retained on the tube runs of theopposite ends of said second reverse bend being equally spaced with theadjacent inner fins retained on the tube runs defined by the oppositeend of said second reverse bend, the spacing between the inner finsretained on the tube runs of the opposite ends of said first reversebend being greater than the spacing between the inner fins retained onthe tube runs of the opposite end of said second reverse bend.
 11. Themethod of forming an evaporator according to claim 8 wherein said stepof bending said tube further comprising bending said tube such that thetube runs defined by the opposite ends of a reverse bend are off-set toprovide a staggered tube pattern.
 12. The method of forming anevaporator according to claim 8 further comprising the steps ofproviding an outer fin having a length greater than the overall lengthof the column of tube run and inserting said tube with inner finsattached into said outer fin.
 13. A method of forming an evaporatorcomprising the steps of: providing a continuous tube; bending saidtubing into a serpentine tube pattern; said serpentine tube including atleast one column of parallel tube runs, each tube run defined by atleast one reverse bend; providing a plurality of inner fins, each saidinner fin having at least one slot; providing a fin fixture having atleast one channel, said channels having a plurality of fin retainerformed therein; inserting and retaining said inner fins in said finretainers, wherein the slots in adjacent inner fins are aligned andoriented in identical directions to receive said reverse bend of saidreverse bend of said serpentine tube; inserting at least one reversebend of said serpentine tube through said aligned set of slots in saidplurality of inner fins retained in said fin retainer; removing saidinner fins having said serpentine tube inserted therein from said finfixture.
 14. The method of forming an evaporator according to claim 13wherein said fin fixture has a first and second channel wherein the finretainers of said first channel are offset from the fin retain retainersof said second channel.
 15. The method of forming an evaporatoraccording to claim 13 further comprising the step of providing an outerfin and inserting said serpentine tube into said outer fin.
 16. Themethod of forming an evaporator according to claim 13 wherein said finretainers formed in each channel are equally spaced.
 17. The method offorming an evaporator according to claim 16 wherein said fixture has afirst channel and a second channel, the spacing between the finretainers of said first channel being greater than the spacing betweenthe fin retainers of said second channel.
 18. A method of forming anevaporator comprising the steps of: providing a continuous tube; bendingsaid tubing into a serpentine tube pattern; said serpentine tubeincluding at least one column of parallel tube runs, each tube rundefined by at least one reverse bend; providing a fin fixture having atleast one channel, said channels having a plurality of fin retainerformed therein; providing a continuous strip of fins for each saidchannel, said continuous strip of fins comprising a plurality of innerfins, said each inner fin having at least one slot; separating saidinner fins; inserting and retaining said inner fins in said finretainers, wherein the slots in adjacent inner fins are aligned andoriented in identical directions to receive said reverse bend of saidserpentine tube; inserting at least one reverse bend of said serpentinetube through said aligned set of slots in said plurality of inner finsretained in said fin retainer; removing said inner fins having saidserpentine tube inserted therein from said fin fixture.
 19. The methodof forming an evaporator according to claim 18 wherein said fin fixturehas a first and second channel wherein the fin retainers of said firstchannel are offset from the fin retain retainers of said second channel.20. The method of forming an evaporator according to claim 18 furthercomprising the step of providing an outer fin and inserting saidserpentine tube into said outer fin.
 21. The method of forming anevaporator according to claim 18 wherein said fin retainers formed ineach channel are equally spaced.
 22. The method of forming an evaporatoraccording to claim 21 wherein said fixture has a first channel and asecond channel, the spacing between the fin retainers of said firstchannel being greater than the spacing between the fin retainers of saidsecond channel.